The Effect of Chronic Overfeeding on Physical Activity in Mice
Abstract
Physical inactivity, together with poor nutrition, make up the second leading cause of death in the United States, and also contribute to the development of a host of diseased states. While strong evidence suggests only modest increases in daily activity is required to decrease all-cause mortality and premature death, activity levels in the U.S. remain low. Indirect results suggest that chronic overfeeding decreases physical activity, though the mechanisms linking overfeeding and decreased activity remain uninvestigated. The most potent biological regulators of daily activity known thus far are the primary sex hormones, and there are reports that chronic overfeeding alters sex hormone levels. Thus, these separate data sets lead to the hypothesis that the primary sex hormones directly link chronic overfeeding and reduced activity. To investigate this hypothesis, inbred mice (C57Bl/6J) were bred, and the resulting offspring were weaned at three weeks of age and randomly assigned to either a control (CFD) or high fat/high sugar (HFHS) diet. Daily wheel running activity (distance, duration, and speed) of the mice was measured along with weekly measurements of nutrition intake and body composition. Upon sacrifice, blood samples were extracted via a cardiac puncture for determination of testosterone and 17β-estradiol levels in male and female mice, respectively.
The mice on the HFHS diet showed a significantly increased daily caloric intake and percent body fat composition. Additionally, the HFHS diet significantly reduced acute wheel running distance for both male and female mice (≈61%). The HFHS-induced reduction in distance was the result of different mechanisms in the male and female mice; the reduction in activity in males due to reduced activity duration, and in females, a decreased speed of activity. A two-week period of wheel access was not sufficient to alter HFHS-induced reductions to activity or increases in body fat. Further, there were no significant effects of chronic overfeeding on serum levels of testosterone or 17β-estradiol, suggesting that the overfeeding-induced decrease in activity occurred independently of sex hormone levels. In conclusion, chronic overfeeding significantly decreases daily activity in mice and shows sexual dimorphism in responsible indices.
Citation
Vellers, Heather Leigh (2016). The Effect of Chronic Overfeeding on Physical Activity in Mice. Doctoral dissertation, Texas A & M University. Available electronically from https : / /hdl .handle .net /1969 .1 /174244.